Percutaneous bypass graft and securing system

ABSTRACT

A bypass graft incorporates fixation mechanisms at its opposite ends, for securing these ends to different locations along a blood vessel, or alternatively to different locations wherein one of the locations is a different vessel or an organ defining a cavity. Mechanical fixation features such as collets or grommets can be employed, enhanced by delivery of an electrical current sufficient to heat surrounding tissue to form a thermal bond. A graft deployment system includes a tissue dilator and a needle for perforating tissue, mounted coaxially within the dilator. Intralumenal systems further include a catheter for containing the dilator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/903,219, entitled “Percutaneous Bypass Graft and Securing System”filed Jul. 10, 2001, which is a continuation of U.S. patent applicationSer. No. 09/415,776, entitled “Percutaneous Bypass Graft and SecuringSystem” filed Oct. 8, 1999 (now U.S. Pat. No. 6,293,955), which is con'tof U.S. patent application Ser. No. 08/966,003, entitled “PercutaneousBypass Graft and Securing System”, filed Nov. 7, 1997 (now U.S. Pat. No.5,989,276), and claims benefit to U.S. Provisional Application Ser. No.60/030,733 entitled “Percutaneous Bypass Graft and Securing System”,filed Nov. 8, 1996.

BACKGROUND OF THE INVENTION

The present invention relates to grafts implantable to bypass anobstruction or other undesirable condition within a vessel or othertubular organ, and more particularly to systems for deploying suchgrafts and fixation elements for securing them.

Bypass grafts are particularly useful in treating vascular diseases, buthave other applications including treatment of urinary incontinence,infertility, and gastrointestinal defects such as occlusions and ulcers.Stenosed vessels cause ischemia which potentially leads to tissueinfarction. Conventional techniques to treat partially occluded vesselsinclude balloon angioplasty, stent deployment, and surgery to attach agraft to bypass the stenosed lesion. Surgical implantation of a bypassgraft typically requires performing a thoracotomy, placing the patienton a cardiopulmonary bypass system, and using cardioplegia to inducecardiac arrest. This permits a suturing of the graft between cardiacvessels without the risk of excess blood loss or the need to accommodatemotion of the heart. Less invasive attempts at positioning bypass graftsinvolve a thoracostomy to produce a conduit to the stenosed lesion. Thisapproach uses endoscopic visualization to position the graft. Thedelivery for such graft requires modified surgical instruments (e.g.,clamps, scissors, scalpels, etc.) and further involves ports insertedthrough small (approximately one inch) incisions to provide access intothe thoracic cavity.

There remains a need for a minimally invasive technique for deployingand securing a bypass graft, and for a fixation means for more reliablysecuring a graft without the need to suture the graft.

Accordingly, it is an object of the present invention to provide asystem for translumenal deployment of a bypass graft.

Another object is to provide a more effective fixation means forsecuring a deployed bypass graft.

A further object is to provide a system for bypass graft deployment, inwhich features incorporated within the graft reduce the time anddifficulty of deployment.

Yet another object is to provide an improved process for deploying andsecuring grafts along body lumens to bypass obstructions and otherundesirable features within the lumens.

SUMMARY OF THE INVENTION

To achieve these and other objects, there is provided a body implantablegraft. The graft includes a tubular graft wall having opposite first andsecond open ends. The graft defines a fluid flow lumen between theseends. The tubular graft is adapted for a selected placement with thefirst end at a first location in body tissue and the second end at asecond location in body tissue, to provide a fluid flow path between thefirst and second locations to bypass an obstruction between thoselocations. The graft also includes a graft fixation mechanism operableto heat the graft wall at least near the first end following placement,to thermally secure the graft wall and adjacent tissue.

The preferred fixation apparatus is an electrically conductive heatingelement mounted to the graft wall near the first end. The element can beannular, and may incorporate a feature to mechanically secure the graft,e.g., a collet or a grommet.

In similar fashion an electrically conductive heating element or otherfixation apparatus can be used to secure the second end of the graft atthe second location. The heating elements can be coupled to an RF powersource and used in conjunction with an indifferent electrode, to securethe graft by ohmic heating.

Another aspect of the invention is a system for deploying a bypassgraft. The system includes an elongate and flexible carrier having aproximal end and a distal end. The carrier is insertable by the distalend for intralumenal movement toward a selected site along a body lumenwhile the proximal end remains outside the body. A tissue perforatingmechanism, near the distal end of the carrier, is positionable at afirst location near the selected site, and operable from the proximalend of the carrier to form a first opening through tissue at the firstlocation. Further, the mechanism is positionable at a second locationnear the selected site and operable to form a second opening throughtissue at the second location. An elongate graft guide, supported by thecarrier and disposed near the distal end, is movable into a guidingposition in which the guide extends from the first location through thefirst opening to the second location and through the second opening. Thesystem further includes a tubular graft adapted to be mounted to thecarrier for movement along the carrier. A graft controller is operableto move the graft distally along the carrier toward the graft guide, andthen distally along the graft guide when the guide is in the guidingposition, to a bypass location in which the graft extends from the firstlocation to the second location and also extends through the first andsecond openings.

The preferred carrier is a catheter having a catheter lumen. An elongatedilator is contained slideably within the lumen, and has a tapereddistal tip. An elongate needle is slideably contained within thedilator.

According to one embodiment, the dilator provides the graft guide, whilethe tissue perforating mechanism includes the needle and the distal tipof the dilator.

According to another embodiment, a distal end region of the catheterprovides the graft guide. The dilator and needle are used to perforateand dilate tissue to form the first and second openings. The dilator isnot used to guide the graft, but is used to guide the catheter,particularly the distal end region which in turn is used for positioningthe graft after withdrawal of the dilator.

According to another aspect of the present invention, an alternativesystem is provided for implanting a bypass graft without the need for acatheter. This system includes a tissue dilating member having at itsdistal end a tissue dilating tip converging in the distal direction. Atissue puncturing tool is supported within the dilating member andextends in the distal direction from the dilating tip. The tool isadapted to puncture or perforate a tissue wall to form an orificeenlargeable by the dilating tip. The system includes a graft with asubstantially fluid impervious graft wall. First, second and thirdopenings are formed through the graft wall at first, second and thirdspaced-apart regions of the wall, respectively. The graft is adapted fora removable mounting on the dilating member in which the dilating memberextends through the first and third openings, with the first openingnear the dilating tip and the third opening proximally of the firstopening. This enables use of the dilating member to insert the firstregion of the graft wall into a first orifice in the tissue wall, forfixation of the first region in the first orifice. The graft further isslideable relative to the dilating member to permit a proximalwithdrawal of the dilating member from the first region after itsfixation, and further to allow an insertion of the dilating member intothe second opening for securing the second region of the graft wallwithin a second orifice in the tissue wall. As a result, the graftprovides a fluid flow conduit between the first orifice and the secondorifice. A closure mechanism is provided for closing the third opening,following withdrawal of the dilating member from the graft, after thefirst and second regions have been secured.

Another aspect of the present invention is a process for translumenallydeploying a bypass graft, including the following steps:

a. advancing an elongate catheter intralumenally toward a selected sitealong a body lumen;

b. with a distal end of the catheter near the selected site, using atissue perforating mechanism mounted near a distal end of the catheterto form a first opening through a tissue wall defining the body lumen;

c. advancing tissue perforating mechanism through the first opening, andthen to a selected location spaced apart from the first opening, thenusing the mechanism to form a second opening through tissue at theselected location;

d. advancing a graft guide through the first opening, distally to theselected location, then through the second opening;

e. with the graft guide so positioned, advancing a tubular graft alongthe guide to a bypass location in which the graft extends from the firstopening to the second opening and through the first and second openings,thus to form a bypass conduit in fluid communication with the bodylumen; and

f. while maintaining the graft in the bypass location, proximallywithdrawing the catheter, the tissue perforation mechanism and the graftguide.

Thus, in accordance with the present invention, bypass grafts aredeployed more easily using techniques that are considerably lessinvasive, and upon deployment are more reliably secured.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the above and other features andadvantages, reference is made to the following detailed description andto the drawings, in which:

FIG. 1 is a side view, partially in section, of a bypass graftconstructed according to the present invention an d secured within avessel;

FIGS. 2-7 illustrate alternative couplings for mechanically fixing theopposite ends of bypass grafts;

FIG. 8 illustrates an alternative embodiment graft incorporatingstructural supports;

FIGS. 9-16 illustrate alternative embodiment grafts incorporatingvalves;

FIGS. 17 and 18 are side sectional views of a bypass graft and systemfor securing the graft to a vessel wall, in accordance with the presentinvention;

FIGS. 19 and 20 illustrate tissue dilators of alternative embodimentdeployment systems employing thermal bonding;

FIG. 21 is a schematic illustration of a circuit for thermal bonding;

FIGS. 22-25 illustrate alternative embodiment dilators;

FIG. 26 illustrates a tissue perforating needle used with the dilatorsof the various deployment systems;

FIG. 27 is a sectional view of a needle and dilator contained within acatheter;

FIG. 28 illustrates an alternative embodiment dilator within a catheter;

FIGS. 29a-h illustrate a series of steps of a percutaneous deploymentand fixation of a bypass graft according to the present invention;

FIGS. 30a-d illustrate an alternative deployment and fixation procedure;

FIGS. 31a-c illustrate a further alternative deployment and fixation;

FIG. 32 shows several bypass grafts secured to the heart; and

FIGS. 33 and 34 illustrate an alternative graft secured within a vessel.

DESCRIPTION OF THE INVENTION

Turning now to the drawings, there is shown in FIG. 1 a bypass graft 16secured within a blood vessel 18, in a manner to bypass a lesion 20within the vessel. Bypass graft 16 has a tubular wall 22 formed of agraft material, e.g., a polymer such as PTFE, urethane, polyimide,nylon, silicone, or polyethylene. The polymer may be extruded, blowmolded, or dipped, and formed either directly into a tubing, or formedfirst as a sheet having opposed ends or edges bonded together to providethe tubular configuration. The edge bond can be formed by a variety ofmethods including ultrasonic welding, thermal bonding, sewing,adhesives, or with radio frequency (RF) energy. Alternatively, the graftcan be a saphenous vein or other vessel from the patient.

At its proximal end 24, bypass graft 16 incorporates a radiallyexpandable stent 26. The graft incorporates a similar stent 28 at itsdistal end region 30. Once graft 16 is deployed, the stents are radiallyexpanded using a dilatation balloon or a mechanism such as thosedescribed in co-pending patent application Ser. No. 08/911,838 entitled“Mechanical Stent and Graft Delivery System,” filed Aug. 15, 1997.Alternatively, the graft end regions can have a self-expandingstructure, as described in co-pending patent application Ser. No.08/932,566 entitled “Radially Expanding Prostheses and Systems for TheirDeployment,” filed Sep. 19, 1997. In either event, each stent and itssurrounding graft material are expanded into intimate contact with wall22 of vessel 18, thus to secure the graft.

As seen in FIG. 1, graft 16 bypasses lesion 20, in the sense that amedial region 32 of the graft is disposed outside of vessel 18. Forconvenience, the graft can be considered to exit the vessel at an exitopening or orifice 34 through vessel wall 35, and re-enter the vessel ata return opening or orifice 36.

Tubular bypass grafts such as graft 16 can be secured within vesselwalls or to other tissue by a variety of fixation mechanisms other thanexpandable stents. For example, FIG. 2 illustrates an annular collet 38attached to one end of a graft 40. The collet may be laminated or bondedto the graft, and is pre-formed to have a segment 42 extending radiallybeyond the graft. Segment 42 also is collapsible into a low profile tofacilitate introduction through vasculature and deployment through thevessel wall. When released, the collet assumes the pre-formedconfiguration as shown. A portion 44 of the graft may extend alongcollet segment 42 to secure the vessel wall between the graft materialand the collet and provide additional support for attaching the graft tothe vessel.

FIGS. 3 and 4 illustrate a collet 46 in which the radially extendingcollet segment is comprised of eight radially extended collet members48. A membrane 50 may be joined to the collet members to prevent fluidflow through the tissue wall puncture site.

FIG. 5 shows a further alternative support mechanism in the form of anannular grommet 52 secured to end region 54 of a graft 56. The grommetincorporates a convergence 58 to facilitate insertion through a vesselwall orifice, and a necked down feature 60 to capture the vessel wallimmediately about the orifice.

As yet another mechanical fixation alternative, flexible bands 62 can befixed to an end region of a graft 64 as shown in FIGS. 6 and 7. Eachband or other flexible member is compressible into the reduced profileshown in FIG. 6 and remains in that profile while constrained, e.g., bya surrounding catheter. When the graft is released from the catheter,band 62 assumes the radially enlarged, more circular profile shown inFIG. 7. Pluralities of such bands can be provided in crossing patternsat the graft ends, if desired.

For increased strength, particularly where a bypass graft is required toexert a radially outward force against a stenosed lesion, a blood vesselwall or other tissue, the graft can incorporate structural supportmembers 66. The support members can be constructed of metal or a polymerhaving a higher modulus of elasticity than the graft material. As shownin FIG. 8, support members 66 can be distributed throughout the graft,with a greater density at the graft end regions to enhance fixationwithin openings through tissue. Support members 66 can have ellipticalor rectangular profiles that enhance their strength in a selecteddirection.

If desired, such support members can be used in lieu of stents 26 and 28for securing graft ends within a vessel. The support members may belaminated in the graft material. Fabrication can involve extruding ordipping an initial graft layer, winding the support members on thelayer, then extruding or dipping to form a second layer covering thesupport members. Alternatively, the separate layers may be bondedtogether, or support members may be threaded through the graft material.

If desired, thermal bonding may be employed to augment the mechanicalfixation and form a more positive fluid seal. More particularly,electrode strips 68 are mounted to the graft near the graft ends, andcoupled through wires 70 to an energy source (e.g., an RF generator)which generates a current to heat adjacent tissue. When sufficientenergy is supplied to the electrodes, the graft edges are thermallysecured to the vessel all by a coagulation of the tissue to theelectrode, or by desiccation of the vessel wall to provide aninterference fit between the reduced-diameter vessel and the graft,especially where the graft and support members exert a radial force.This better secures the graft to the vessel wall and prevents leaks atthe graft edges. Suitable materials for the electrodes, which are bodycompatible as well as electrically conductive, are platinum,platinum-iridium, stainless steel, and gold.

Once the graft has been sealed, signal wires 70 are removed from thegraft by delivering a D.C. current through the signal wires at anamplitude sufficient to cause a breakdown of the signal wire, e.g., at areduced-diameter weak point near its associated electrode.Alternatively, the signal wire can be cleaved, or mechanically removedby applying tension to sever the wire at a reduced-diameter neck region.

On occasion, it is desirable or necessary to ensure that flow of bloodor other fluids through the graft is uni-directional. To this end, avalve may be placed within the graft, preferably along the medialregion. FIGS. 9-16 show a variety of graft constructions.

Turning first to FIGS. 9 and 10, a valve 72 includes a valve ball 74within a surrounding structure that provides a valve seat 76 on one sideof the ball, and upper and lower retainers 78 and 80 on the other sideof the ball. In FIG. 9, the valve is open and allows flow in thedirection of the arrows, around the valve ball and through open spacesbetween the valve ball and surrounding structure in the area notoccupied by the upper and lower retainers.

As shown in FIG. 10, flow in the opposite direction is substantiallyprevented by a lodging of ball 74 against the valve seat. Further, thevalve functions as a pressure relief valve in that the flow from left toright as viewed in the figure must be sufficient to overcome thetendency of retainers 78 and 80 to urge the ball valve against the valveseat.

FIG. 11 shows a valve 82 designed to react to the muscular contractionto restore normal vessel function. Muscular contraction forces the valveends inward, opening the valve to permit fluid flow. The force requiredto open the valve may be selected, depending on the material, wallthickness, length, and geometry. A solid valve requires more force thana valve in which material is selectively removed to maintain the valvefunction yet decrease the required compressive force to open the valve.

FIGS. 12-14 show a one-way valve 84 having a membrane 86 that closesover valve support struts 88 when no external pressure is present. Whenpressure is applied due to a fluid flow, membrane 86 distends outwardlyaway from the struts as seen in FIG. 14, permitting the flow of fluids.Fluid flow in the opposite direction (right to left as viewed in FIGS.12 and 14) is prevented.

The valves in FIGS. 9-10 and 12-14 act as pressure relief valves, in thesense that they may be tailored to require a selected force to openthem, and they remain open only when the applied pressure exceeds thevalve resistance. As a result, these valves characteristically remainopen for short periods of time. Alternatively, FIGS. 15 and 16 show apressure relief valve 90 that opens due to pressure exerted on thevalve, and remains open until a compressive closure force is applied.Valve 90 includes a plunger 92 movable within a surrounding structureincluding a valve seat 94 and a knob structure 96 for retaining thevalve against the valve seat. The outer structure, which can be thegraft itself, includes a flexible section 98 including a protrusion 100that can be flexed radially inwardly responsive to external pressure.

The knob structure maintains the valve closed until pressure against thevalve, i.e., acting from left to right as viewed in FIG. 16, exceeds aselected threshold and opens the valve to allow rightward flow. Evenafter such pressure subsides, the valve remains open until external,radially inward pressure is applied to compress flexible section 98 ofthe graft. This moves the plunger leftward, returning it beyond the knobstructure against the valve seat, thus closing the valve once again.

Valve 90 is particularly well-suited for treating urinary incontinence.When bladder pressure exceeds the relief valve pressure threshold, thevalve is opened to permit the flow of urine. When the bladder pressureis relieved, muscular contractions or other external squeezing flexessection 98 to return plunger 92 to the valve seat, thus closing thevalve.

Systems for deploying grafts may require an incision, or alternativelymay involve translumenal delivery for a substantially noninvasiveprocedure. In the latter case, the system must restrain the graft duringintroduction through sheathes positioned via the Seldinger technique ora surgical cut-down, advancement through the vasculature and into thetarget vessel. Unwanted perforations of the vessel or other tissue mustbe avoided. This requires flexibility to follow a guide wire positionedin the target vessel. Further, the system must facilitate easy andaccurate deployment of the graft and delivery components. If a partiallydeployed graft needs to be altered as to location, the system shouldpermit recapture and repositioning. Graft delivery systems mayincorporate the capacity to mechanically create intimate contact of thegraft with surrounded tissue, especially at the graft ends. Thiscapability is discussed in the aforementioned application Ser. No.08/911,838 entitled “Mechanical Stent and Graft Delivery System.”

FIGS. 17 and 18 show a bypass graft deployment system 102 that requiresan incision. The system includes a dilator 104 having a tapered(distally converging) distal tip 106. A needle 108 is mounted coaxiallywithin the dilator, and has a sharp cutting edge 110 for puncturing orperforating tissue. A bypass graft 112, having a grommet 114 or othersuitable fixation mechanism, is supported on and surrounds the dilator.

Use of system 102 requires an incision characteristic of a surgicalcut-down, through the dermal layers near the vessel to provide aninsertion port. Needle 108, which can be slideably contained within thedilator if desired, is introduced into the insertion port and puncturesa wall 116 of a vessel 118 on one side of a stenosed lesion 120. Thedilator then is advanced over the needle to enlarge the puncture toprovide an orifice for fixation of the graft. At this point, graft 112is advanced over the dilator sufficiently to position grommet 114 withinthe orifice. Thus, a first region 122 of the graft is secured, so thatan opening 124 of the graft is in fluid communication with vessel 118.

As seen in FIG. 18, graft 112 has two further openings: an opening 126surrounded by graft material and a second grommet 128; and a moreproximally disposed opening 130, where no grommet or other fixationdevice is provided.

Progress from the view of FIG. 17 to the view of FIG. 18 involves, inpart, securing region 122 and grommet 114 as just described. Next,dilator 104 and needle 108 are withdrawn proximally, sufficiently toremove them from region 122. Then, the dilator and needle are distallyinserted through opening 126, to become surrounded by grommet 128 and agraft region immediately about opening 126 as shown in FIG. 18. At thispoint, needle 108 is advanced to puncture tissue wall 116, and dilator104 is used to enlarge the puncture, to form a second orifice on theopposite side of lesion 120. Then, as shown in FIG. 18, the dilator andgraft are advanced sufficiently to position grommet 128 within theorifice.

After grommet 128 is secured, the dilator and needle are withdrawn fromopening 126, and further are withdrawn from a region 132 of the graftsurrounding opening 130 so that the dilator and needle are completelyfree of the graft. Then opening 130, which is provided only to allowaccess of the dilator and needle, is closed to prevent fluid leakagefrom the graft. One suitable closure mechanism is a purse-string, formedby threading a suture through the graft material in region 132. Otherclosure mechanisms include staples or adhesives.

In multiple lumen applications, the bypass graft may have four or moreopenings to accommodate three or more fluid couplings to vasculature ororgan cavities.

Alternative embodiment deployment systems use different approaches forgraft fixation. For example, FIG. 19 shows a dilator 136 with a centrallumen 138 for a needle (needle not shown). The dilator also incorporatesa lumen 140, through which a signal wire can extend for coupling with adilator electrode 142. Electrode 142 delivers RF energy to a grommet 144at the distal end of a graft 146 surrounding the dilator, thus tothermally secure the grommet to a tissue wall 148 of a vessel 150.

In FIG. 20, a dilator 152 includes, along with a central needle lumen154, a signal wire lumen 156 and a balloon inflation lumen 158 open to aballoon 160 near the distal end of the dilator. The dilator supports asurrounding graft 162 having a collet 164 at its distal end.

Following insertion of the dilator through wall 166 of vessel 168,balloon 160 is inflated to temporarily secure the dilator, which alsobends a portion of collet 164 into the retaining position as shown. Anelectrode 170, mounted on the exterior of balloon 160, receives acurrent from a signal wire contained in lumen 156, for thermally bondingcollet 164 to the surrounding tissue. After thermal bonding, the balloonis deflated and the dilator withdrawn.

FIG. 21 illustrates a schematic circuit for ohmic heating of tissue,useable in conjunction with electrode 170, other dilator supportedelectrodes, or electrodes mounted directly to a graft as previouslydescribed. An RF power generator 174 is coupled to the electrode througha signal wire 176. An indifferent electrode 178, spaced apart fromelectrode 170 and typically placed on a patient externally, is coupledto the RF generator through a conductor 180. Thus, a current isgenerated through tissue between electrodes 170 and 178, heating thetissue to form the bond.

FIGS. 22 and 23 are sectional views of a distal region of a dilator 182,taken at different angles to show different lumens through the dilator.Lumens 184 and 186 in FIG. 22 accommodate signal wires to sensors ortransducers 188 and 190 (further discussed below), which can be used todirect placement of the dilator at puncture sites. Sensor 188 ispositioned for axial sensing, while a sensor 190 is oriented for lateralsensing. Several sensors 190 can be angularly spaced apart from oneanother about the dilator circumference.

Lumens 192 and 194, shown in FIG. 23, accommodate signal wires 196 toelectrodes 198 used for thermal bonding.

As shown in FIG. 24, a steering mechanism can be incorporated into thedilator to facilitate positioning of the dilator and needle for tissueperforations. In particular, a ring 198 is embedded in the dilatordistal tip, surrounding needle lumen 200. A wire 202 is attached to ring198. By pulling wire 202, the distal tip can be biased downwardly asviewed in the figure.

To further assist positioning, magnets may be incorporated into thedilator near its distal tip, as indicated at 206 for a dilator 208 shownin FIG. 25. Such magnets may be formed of ferrite materials, oralternatively may be formed by winding conductive coils around thedilator to form electromagnets when current is supplied. The dilatormagnets are used in conjunction with a guide wire 209 advanced beyond astenosed lesion 210 within a vessel 212. The guide wire is formed ofmetal, and to further enhance magnetic attraction may incorporate amagnet 214 of opposite polarity to the dilator magnet. Magneticpositioning facilitates placing bypass grafts through tortuous vesselsor over long distances beyond the lesion. Alternatively, known imagingtechniques can be used to locate the dilator magnets.

As seen in FIG. 26, a needle also can be provided with steeringcapability, in particular by forming a hollow needle 216 and securing awire 218 to a distal portion of a needle through a weld or solder joint220. A sensor 222 at the needle tip, coupled to wires 224 containedwithin the needle lumen, can be used to sense a position of the needletip. A further needle enhancement is a stop 226. When open as shown inFIG. 26, stop 226 limits the degree to which needle 216 can be insertedinto tissue, thus preventing excessive, damaging perforations. At thesame time, stop 226 is collapsible into a diameter substantially thesame as that of the needle when the needle is withdrawn into a dilator.

Intralumenal graft deployment systems also utilize dilators and needlesas described, but further incorporate catheters. A suitable arrangement,as shown in FIG. 27, includes a needle 228 surrounded by a dilator 230,which in turn is surrounded by a catheter 232, all components beingcoaxial and circular in profile.

An alternative arrangement, shown in FIG. 28, incorporates non-circularfeatures into a dilator 234 and a lumen of a catheter 236. Thenon-circular matching features allow transmittal of torque from catheter236 to dilator 234, enabling selective rotation of the dilator byrotating the catheter.

FIGS. 29a-29 h illustrate progressive steps in a percutaneous,intralumenal deployment of a graft 238, to bypass a lesion in a vessel240. The system includes a catheter 242 with a lumen 244 containinggraft 238, a dilator 246 and a needle 248 within the dilator.

First, the catheter and other components are advanced intralumenally tothe proximal side of lesion 250 as shown in FIG. 29a. Sensors 252facilitate positioning. Such sensors can include ultrasonic transducersof piezoelectric material, infrared transducers, or fiber-opticelements. Alternatively, a radiopaque contrast material may be injectedto enhance fluoroscopic visualization.

As seen in FIG. 29b, needle 248 is advanced to puncture vessel wall 254.A stop 256 restricts movement of a needle if necessary. Then, dilator246 is advanced, collapsing stop 256 and enlarging the puncture toprovide a suitable orifice through the vessel wall. The orifice anddilator tend to form a seal, preventing excess blood leakage as thedilator is advanced along and outside of the vessel. The dilator mayhave a pre-shaped distal end to facilitate positioning, as shown in FIG.29c.

When the dilator has been advanced to a point near a selected re-entrylocation, needle 248 is advanced beyond the dilator to puncture vesselwall 254 (FIG. 29d). Once again, stop 256 prevents excessive needleadvancement, if necessary. Alternatively the stop can limit needletravel relative to the dilator. At this point, dilator 246 is advancedover the needle (FIG. 29e), collapsing the stop and enlarging thepuncture by its distal tip, entering the vessel once again. At thistime, needle 248 may be completely retracted if desired.

As seen in FIG. 29f, graft 238 then is advanced over dilator 246, untilthe graft reenters the vessel, i.e., has its opposite ends contained,each in its respective orifice. A collet 258 at the distal end of thegraft prevents graft retraction, and a collet 260 anchors the proximalend of the graft. At this point, the dilator can be retracted back intocatheter 242, as shown in FIG. 29g. A hollow stylet 262 is used toadvance the graft, and also to maintain the graft in place duringsubsequent withdrawal of the dilator. Finally, the catheter, stylet anddilator are withdrawn, leaving graft 238 secured, as seen in FIG. 29h.

FIGS. 30a-d show an Alternative system and graft deployment process, inwhich a graft 264 is guided to its bypass location within a catheterrather than over a dilator. The system includes a catheter 266containing a dilator 268, which in turn contains a puncturing needle270. These components are advanced to a position proximate a lesion 272within a vessel 274. Dilator 268 is pre-formed with a bend at its distalregion, and when positioned as shown in FIG. 30a, is directed upwardlytoward the vessel wall as shown, to direct the needle toward the firstintended puncture.

After puncture and dilation with the dilator tip, dilator 268 can beadvanced over the needle, outside of and along the vessel. The dilatoris rotated, preferably by the catheter using non-circular profilefeatures as described above, to reorient the tip and point it backtoward the vessel as shown in FIG. 30b. Catheter 266 is advanced alongthe dilator, through the orifice and outside of the vessel. A balloon276 surrounding the catheter can be inflated at this point, to maintainthe catheter against proximal withdrawal.

Then, with the tip of dilator 268 positioned against the vessel wall atthe desired puncture location, needle 270 is advanced to form thepuncture for a re-entry orifice (FIG. 30c). The dilator tip is used toenlarge the orifice, permitting advancement of the dilator into vessel274, followed by advancement of catheter 266 over the dilator, throughthe orifice and into the vessel as well. Balloon 276 can be reinflatedat this point, to temporarily secure the catheter.

With the catheter secured, the dilator and needle are withdrawn, leavingthe catheter alone as in FIG. 30d. At this stage, and after withdrawalof the dilator and needle, a graft can be inserted into the catheter andmoved distally along the catheter using a stylet 278, until the graftreaches a bypass location in which each end of the graft is containedwithin its respective orifice. Withdrawal of the catheter (not shown),while the stylet maintains the graft in the bypass location, allowscollets or other fixation mechanisms to expand and secure the graft.

This procedure is particularly suited for smaller lesions, where thedilator need travel only a short distance along the vessel.

FIGS. 31a-c illustrate a further alternative system and procedure forforming a bypass from a vessel to an organ cavity. Initially, a catheter280 containing a dilator 282 and a needle 284 is advanced to an intendedpuncture site 286 within a vessel 288. The puncture is formed aspreviously described, and the dilator is advanced through tissue to anorgan cavity 290. Then, the catheter is advanced over the dilator,becoming open to the cavity as shown in FIG. 31b. This permits use of astylet 292 to advance a graft 294 through the catheter, until thecatheter extends completely through the tissue to the cavity. Collets293 and 295 secure the catheter. A valve 296 within the catheter limitsflow to the direction indicated by the arrow. A graft 298 incorporatinga valve 300 is positioned near lesion 302, to prevent backflow towardthe lesion.

FIG. 32 illustrates two bypass grafts 304 and 306 used to couple theaorta to coronary vasculature in accordance with the present invention.

FIG. 33 illustrates a graft 306 collapsed around a catheter body 308,deployed in a target vessel across a stenosed lesion 310. The catheterand graft are translumenally advanced to the position shown. Theopposite ends of the graft contain expandable stents 314 and 316,expanded in place with a mechanism such as those described in theaforementioned application Ser. No. 08/911,838. Alternatively, the graftends can have self-expanding characteristics.

FIG. 34 shows the graft expanded. The ends are fully expanded intointimate contact with the vessel wall. However, along a medial region318, graft 306 is expanded only to a nominal diameter. The diameter isselected to reduce the flow of resistance and increase cardiac output,yet prevent damage to the endothelial wall. For example, a 50% expansionusually is sufficient to open the vessel while preventing excess damage.A large space between the exterior of the graft and the vessel wallaccommodates growth of the stenosed lesion, and tends to contain suchgrowth along the vessel wall so that the vessel remains open. Toaccomplish this, graft 308 should have inherent radial stability, forexample, by employing structural supports as previously discussed.

If desired, graft structural stability and fixation can be enhanced byforming grafts with two or more layers, with pockets formed between thelayers to contain biocompatible foams which solidify when activated toprovide further support. Drug solutions also can be provided in suchpockets.

To improve graft radial expansion in conjunction with using the graft ofFIGS. 33 and 34, channels may be formed through the lesion by cutting aslit through the vessel wall in the targeted region. A mechanicaldeployment system as described in the aforementioned patent applicationSer. No. 08/911,838 can be used to form the required channel.

Thus, in accordance with the present invention, a more easily deployedgraft is more reliably secured, to effectively bypass lesions and otherblockages.

The patent applications cited herein are incorporated by reference, eachin its entirety and for all purposes.

We claim as our invention:
 1. An anastomotic connector for connecting atubular graft to a blood vessel or hollow body organ comprising anannular collet having a proximal end adapted to be secured to the graftand a distal end adapted to be secured into the blood vessel or hollowbody organ, the distal end having a preformed radially outwardlyextending segment having a preformed configuration which is collapsibleinto a low profile but when released assumes the preformedconfiguration, said radially extending segment having a plurality ofcircumferentially spaced apart radially extending collet members, saidradially extending collet members having non-tissue penetrating outerextremities, said collet members being adapted to underlie the interiorof the vessel wall and engage the vessel wall to aid in retaining thedistal extremity of the connector within the vessel or body organ.
 2. Ananastomotic connector as in claim 1 wherein the annular collet iscomprised of a nickel-titanium alloy.
 3. An anastomotic connector as inclaim 2 wherein the nickel-titanium alloy is a memory elastic material.4. An anastomotic connector as in claim 1 wherein the annular collet iscomprised of a material selected from the group consisting of stainlesssteel and thermoset plastic.
 5. An anastomotic connector as in claim 1wherein the graft is laminated to the collet.
 6. An anastomoticconnector as in claim 1 wherein the graft is bonded to the collet.
 7. Ananastomotic connector as in claim 1 wherein the graft is joined to thecollet over an outer surface of the collet proximal end and overlaps theblood vessel or hollow body organ.
 8. An anastomotic connector as inclaim 1 wherein the radially extending collet members form an angle withthe collet proximal end of between about 45° and 120° when in thepreformed configuration.
 9. An anastomotic connector as in claim 8wherein the angle is about 90 degrees.
 10. An anastomotic connector asin claim 1 wherein the radially extending collet members engage thevessel wall interior by direct contact without penetrating the vessel ororgan wall interior.
 11. An anastomotic connector as in claim 1additionally comprising a membrane disposed about at least a portion ofthe collet members.
 12. An anastomotic connector as in claim 11 whereinthe membrane is at least partially impervious to fluid flowtherethrough.
 13. An anastomotic connector as in claim 11 wherein themembrane forms a continuous, annular, fluid-impervious layer.